Methods for producing cathode and all-solid-state battery

Abstract

Provided is a method for producing a cathode that is configured to decrease battery resistance when it is used in an all-solid-state battery. The cathode includes a cathode layer containing composite cathode active material particles and solid electrolyte particles. At least one of the composite cathode active material particles and the solid electrolyte particles contain a sulfur element. In a photoelectron spectrum by X-ray photoelectron spectroscopy measurement of the cathode layer, an S peak intensity ratio (C/D), which is derived from the sulfur element, of a signal intensity C at a binding energy of 161.6 eV to a signal intensity D at a binding energy of 163.1 eV, is larger than 0.78.

1 . A method for producing a cathode comprising a cathode layer for all-solid-state batteries, the method comprising:
 preparing composite active material particles comprising cathode active material particles and a lithium ion conducting oxide coating at least part of the surface of the cathode active material particles, by:
 drying, on the surface of the cathode active material particles, a peroxo complex aqueous solution containing an element that will compose the lithium ion conducting oxide to obtain a precursor of the composite active material particles; and 
 sintering the precursor to obtain the composite active material particles; 
   vacuum-drying the composite active material particles, immediately after the sintering, at a temperature of 120° C. or more and 300° C. or less for one hour or more;   mixing the composite active material particles with solid electrolyte particles to obtain a cathode mix; and   forming the cathode mix to obtain the cathode layer,   wherein:   at least one of the composite active material particles and the solid electrolyte particles contain a sulfur element, and   in a photoelectron spectrum by a X-ray photoelectron spectroscopy measurement of the cathode layer, an S peak intensity ratio (C/D), which is derived from the sulfur element, of a signal intensity C at a binding energy of 161.6 eV to a signal intensity D at a binding energy of 163.1 eV, is larger than 0.78.   
     
     
         2 . The method for producing the cathode according to  claim 1 , wherein in the vacuum-drying, the composite active material particles are vacuum-dried at a temperature of 200° C. or more and 300° C. or less for one hour or more. 
     
     
         3 . The method for producing the cathode according to  claim 1 , wherein the lithium ion conducting oxide is at least one selected from the group consisting of lithium niobate, lithium titanate, lithium lanthanum zirconate, lithium tantalate and lithium tungstate. 
     
     
         4 . The method for producing the cathode according to  claim 1 , wherein the solid electrolyte particles are sulfide-based solid electrolyte particles. 
     
     
         5 . The method for producing the cathode according to  claim 1 , wherein a moisture content of the composite active material particles in the cathode layer is 70 ppm or less. 
     
     
         6 . A method for producing an all-solid-state battery, the method comprising:
 producing the cathode according to  claim 1 ; and   producing the all-solid-state battery, which comprises:
 the cathode comprising the cathode layer, 
 an anode comprising an anode layer, and 
 a solid electrolyte layer disposed between the cathode layer and the anode layer.